Methods for using high-yielding non-Newtonian fluids for severe lost circulation prevention

Abstract

A system and method to model and analyze the mixing energies of high-yielding non-Newtonian fluids to prevent chemical lost circulation is disclosed. Laboratory tests are performed under varying conditions from which data on the mixing energies needed to optimize the use of high-yielding non-Newtonian fluids to prevent lost circulation is obtained. This data is then applied to a non-linear mathematical modeling system that is capable of scaling the data to give a dimensionless value. This value can be combined with historic information to predict optimal flow rates and mixtures to prevent chemical lost circulation. This data may be verified by means of simulation, lab testing, or application to a full-size well.

1. A method of remotely mixing a wellbore fluid and a lost circulation treatment material being pumped into a wellbore where the resulting mixture exhibits non-Newtonian qualities, comprising the steps of:
 determining a mathematical function relating integral shear history to yield point for a mixture of a lost circulation treatment material and a wellbore fluid using bench top testing; 
 modeling downhole integral shear history as a function of flow rate of said lost circulation treatment material being pumped downhole into a given wellbore using a similitude model; 
 using said mathematical function to determine a downhole integral shear history to achieve an acceptable downhole yield point for said mixture; 
 determining a downhole flow rate of said lost circulation treatment material based on said downhole integral shear history and said modeling action; and 
 pumping said lost circulation treatment material downhole into said given wellbore at said determined downhole flow rate. 
 
   
   
     2. The method of  claim 1 , wherein said wellbore fluid and lost circulation material are non-Newtonian fluids. 
   
   
     3. The method of  claim 1 , wherein said modeling action comprises a dimensionless form of analysis. 
   
   
     4. The method of  claim 3 , further comprising the steps of:
 using sensors to update said dimensionless analysis with actual data; and 
 adjusting said downhole flow rate to affect the yield point of said mixture downhole. 
 
   
   
     5. The method of  claim 3 , wherein said the results of said dimensionless analysis comprise a pi mixing number. 
   
   
     6. The method of  claim 1 , further comprising a step of:
 choosing the composition of said lost circulation treatment material to be injected downhole into said given wellbore based on historical data. 
 
   
   
     7. The method of  claim 1 , wherein said lost circulation treatment material is comprised of:
 oil present in an amount in the range of from about 32% to about 62% by weight of said composition; 
 a hydratable polymer present in an amount in the range of from about 3% to about 6% by weight of said composition; 
 an organophillic clay present in an amount in the range of from about 0.3% to about 0.6% by weight of said composition; and 
 a water swellable clay present in an amount in the range of from about 34% to about 62% by weight of said composition. 
 
   
   
     8. The method of  claim 1 , wherein said lost circulation treatment material and said wellbore fluid are delivered by two or more liquid streams, and where one or more streams are delivered through the drillstring. 
   
   
     9. The method of  claim 1 , further comprising the step of:
 choosing said lost circulation treatment material based upon the composition of said wellbore fluid. 
 
   
   
     10. The method of  claim 1 , wherein said lost circulation treatment material is comprised of:
 water present in an amount in the range of from about 6% to about 50% by weight of said composition; 
 an aqueous rubber latex present in an amount in the range of from about 33% to about 67% by weight of said composition; 
 an organophillic clay present in an amount in the range of from about 13% to about 22% by weight of said composition; 
 sodium carbonate present in an amount in the range of from about 2.7% to about 4.4% by weight of said composition; and 
 a biopolymer present in an amount in the range of from about 0.1% to about 0.2% by weight of said composition. 
 
   
   
     11. The method of  claim 1 , wherein an acceptable viscosity is achieved downhole.